1. Field of the Invention
The present invention relates generally to pipeline and vessel connections and more specifically to devices for subsequent connection of, for example, a tie-in line or branch pipe to a carrier pipe. The invention more particularly concerns a tapping flange for connecting branch pipes to carrier pipes, such as subsea carrier pipes used for carrying oil and/or gas.
2. Description of Related Art
When subsea transmission pipelines are laid, side tap assemblies are typically installed at regular intervals for future tie-ins of branch, in-field, or lateral pipelines. For example, in a typical 50-mile long pipeline section, an average of five to six side tap assemblies may be required. However, the relatively high cost of these assemblies and the special handling they require during installation can be problematic and may discourage their use and result in a reduction in number or total elimination of side taps. In those cases where side tap assemblies are not initially installed, later tie-ins may require the installation of costly, subsea-installed, hot tap connectors.
In an effort to reduce the cost of configuring a pipeline for future tie-ins, a blocking flange and removable blocking plug assembly has sometimes been employed. Such a flange and plug assembly may be installed on a tee-type fitting and welded into the pipeline during the pipe laying operation. Using this type of fitting, at the time a tie-in is required, the operator may install a valve on the flange and, using special equipment, reach through the valve to remove the plug. Subsequent to this operation, a special basket may be deployed and locked into the flange to accommodate pigging bars to prevent inadvertent misdirection of a pig.
The disadvantages of the flange and blocking plug assembly approach are numerous. For example, the plug and operating screws of a typical blocking plug mechanism are elastomer sealed. This may result in a significant leak path if the elastomer degrades or is exposed to incompatible fluids. Further, such blocking plugs were originally designed to be temporary blocking devices for pipeline plugging and bypass operations, and therefore were not specifically designed for removal. Consequently, the success of a subsea blocking plug removal operation cannot be assured. Finally, deployment of a blocking plug removal tool and pigging basket installation tool requires additional diving time at considerable expense to the pipeline owner/operator.
To overcome the above described potential for blocking plug leaks, it has been proposed that a blocking flange be welded to a pipe section that is in turn welded to a transmission pipeline wall. The transmission pipeline wall would then be cut out at such time as a lateral connection is required. The problems associated with this approach, however, are also numerous. For example, the weldment of the pipe stub to the main pipeline would have to be a fillet profile, and fillet welds are not generally accepted for pressure containing weldments since they can not be easily inspected. Also, studies have indicated that a branch outlet size should not exceed 50% of the diameter of the main pipeline, and this limitation would be too restrictive in some applications where anticipated branch pipe flow rates would require large piping sizes. Additionally, the stress behavior of the post-tapped joint could not be simulated with traditional hydrostatic pressure testing, and even with this approach, a blocking or similar type flange would be required for installation of a pigging basket to prevent misdirection of pigs and subsequent blockage of the main pipeline. Finally, as noted above regarding removal of a blocking plug, tapping of the main pipeline wall and installation of the basket can be expected to be very costly operations.
In one respect, the present invention comprises a tapping connector for sealing, isolating, and/or tapping containment structures such as pipes, including underwater or surface pipelines. In one embodiment utilized with pipes, the connector is typically installed during pipeline construction to allow future connections to the pipeline.
In another respect, the invention comprises a flange or other bored connector which includes an arcuate membrane or diaphragm, typically an elongated arched membrane whose longitudinal axis or centerline may be generally transverse relative to the axis or centerline of the bore. The membrane or diaphragm typically has a transverse cross-section which is arch-shaped. The ends and sides of the arched membrane or diaphragm typically extend to the walls of the bore and seal the bore. The opposing inner and outer surfaces of the arch may have the same or different curvatures. The curvature of the arch and the thickness of the membrane are typically configured such that the cutter of a boring tool experiences alternate cutting and clearing periods when boring through the membrane. The longitudinal centerline of the arched membrane or diaphragm typically lies generally transverse to the longitudinal centerline of its connector. The outer and inner surfaces of an arcuate membrane each typically define an arc of a circle, but may also individually or together define other curves or mixtures of curves including, but not limited to, parabolic. Thus, a membrane seal of the invention may be configured to resemble a longitudinal segment of a conduit whose ends and side-edges intersect the inner wall surfaces of a conduit to seal off the bore of the connector. The composition of the membrane is such as to be drillable but also strong enough to serve as a seal.
In another respect, the tapping connector, of which the membrane or diaphragm is a part, is typically adapted at each end to be connected to a conduit or a vessel for conveying or otherwise containing fluids. Especially effective applications of the invention lie in tapping a pipeline, storage tank or the like. Advantageously, the connector may form part of an original pipeline, tank, reaction vessel or the like, or it may be added at a later time.
In one embodiment of the tapping connector, a membrane may be defined by opposing surfaces comprising an outer convex surface and an inner concave surface, wherein these outer and inner surfaces are each characterized by a radius of curvature. The membrane may further be defined by a generally linear longitudinal axis or centerline and a generally curved or arched latitudinal axis or centerline. These centerlines are typically approximately perpendicular to one another. The outer and inner membrane surfaces may have similar radii of curvature and therefore be coaxial with one another, in which case the membrane presents an essentially constant cross sectional profile. In another embodiment, the outer, convex surface may be defined by a larger radius of curvature than that of the inner concave surface. In yet another embodiment, the outer, convex surface may be defined by a smaller radius of curvature than that of the inner, concave surface.
In another embodiment, the tapping connector of the present invention may be manufactured such that it is integral with other connectors or connecting devices. For example, the tapping connector of this invention may be integral with a tee connection or a Y-shaped connection. The tapping connector may also be integral with a collet connector apparatus or a boltless flange connector apparatus.
In another broad respect, this invention comprises a method for connecting a first containment structure to a second containment structure. As used herein, the term xe2x80x9ccontainment structurexe2x80x9d refers to any vessel, chamber, container, or other structure suitable for isolating one environment from another, such as for holding, containing, transporting or otherwise serving as a conduit for any liquid, gas, or other fluid, slurry, fluid/solid mixture, or semi-fluid substance, whether used in an above ground, subsea, or other application. Examples of types of such containment structures include, but are not limited to, pipes, pipelines, pipe segments, pipe nipples, tee connections and other connector apparatuses, tubes and/or tubular structures, pressure and process vessels, storage tanks, chambers or other structures. In typical embodiments, a containment structure may be, for example, a carrier pipe, a branch pipe, a tee or Y-connection or fitting, ball valve, collet connector apparatus, boltless flange connector apparatus, etc. In the method of the present invention, one end of a tapping connector is typically joined to, connected to, or integrally formed with a first containment structure (such as integrally formed with a wall of a tank or pipeline). When so installed, the tapping connector thus may serve to isolate the interior of such a first containment structure, for example, by containing any internal pressure, vacuum and/or contents present within the first containment structure. A second containment structure may be optionally joined to, connected to, or formed with the other end of the tapping connector, initially or at a later time. When a second containment structure is so utilized, the tapping connector may serve to isolate the interior of the first containment structure from the second containment structure by, for example, containing any internal pressure, vacuum and/or contents present within either or both of the containment structures. When so desired, isolation or containment may be eliminated by removing the membrane from the connector using conventional tapping tools, for example, to allow the interior of a first containment structure (including any contents, vacuum, and/or pressure that may be present therein) to be exposed to the atmosphere or other environment, or to allow the interiors of first and second containment structures (including any contents, vacuum, and/or pressure that may be present in either or both of the interiors) to be exposed to one another. Such exposure may or may not result in flow or mixture of the contents of a containment structure with the atmosphere, the contents of another containment structure, or another environment. It will be understood with benefit of this disclosure that benefits of the disclosed method and apparatus may also be achieved without removal of the membrane as so described above.
In another typical embodiment, the tapping connector of this invention comprises an apparatus for sealing and/or tapping a containment structure. In this embodiment, the apparatus comprises a connector body having a bore extending between two opposing ends, and it is adapted at one end to connect to the containment structure. An arched membrane or diaphragm is disposed within the bore of the connector body, thus sealing the bore. The membrane or diaphragm comprises a longitudinal segment of a conduit arranged transverse to the bore and intersecting inner surfaces of the connector body.
In another typical embodiment, this invention comprises an apparatus for sealing and/or tapping a containment structure for holding or transporting a fluid. The apparatus comprises a first fitting having first and second ends, wherein the first and second ends define a first bore therebetween. The first end is connected to the containment structure. The apparatus further comprises a second fitting having first and second ends which define a second bore therebetween. The second fitting is connected at its first end to the second end of the first fitting to define a fluid passageway which includes the first and second bores. A membrane or diaphragm is disposed within the bore of one of the fittings, sealing the fitting, and this membrane or diaphragm is positioned to be penetrated from the second end of the second fitting. The membrane or diaphragm forms an elongated, curved arch arranged transversely relative to the bore of the fitting in which it is disposed.
In another embodiment of the invention, one end of a tapping connector is typically joined to a first containment structure. The other end of the tapping connector may then be optionally isolated or covered with an isolation structure, for example, to temporarily isolate or protect it from the elements until it is desired to make a connection to the first containment structure. In this regard, an isolation structure may be any closure means suitable for isolating, covering or protecting the other end of the membrane or membrane connector including, but not limited to, a plug, blind flange, protector flange, etc. When it is desired to make such a connection, the isolation structure may be removed and a second containment structure may then be joined to the other end of the tapping connector. Finally, the membrane of the tapping connector may be conveniently removed using conventional tapping tools.
In one typical embodiment, this invention comprises a tapping connector including a gasket face flange, a weld neck, and a curved or arcuate membrane disposed therebetween. In this embodiment, the curved or arcuate membrane offers a partially cylindrical profile that resembles the wall of a pipe. In this regard, the curved or arcuate membrane typically presents a convex profile oriented toward the gasket face flange side and a concave profile oriented toward the weld neck side. The curved or arcuate membrane is typically cast as an integral part of the flange, although other means of configuring a flange with a curved or arcuate membrane are possible including, but not limited to, shaped or closed-die forgings, a welded-in membrane in a standard weld neck flange or other types of flanges, etc. A sealing groove or other sealing means may be provided on the gasket face flange side of the membrane. Sealing means on the gasket face flange side of the membrane may include, but is not limited to, raised face flanges or seals, ring type joints, or any other sealing means known in the art.
In another embodiment, this invention comprises a method for connecting a branch pipe to a carrier pipe. In this method, a weld neck of a tapping connector embodiment described herein is typically welded to a tee placed in the carrier pipe, such that the convex side of the membrane is presented outward and away from the carrier pipe. A blind flange or protector flange is then typically installed on the gasket face flange side of the tapping connector for protection of the sealing groove of the gasket face flange. When so installed, the membrane blocks the bore of the flange and thus contains the internal pressure and/or contents of the pipeline. Advantageously, when it is desired to make a connection at the tapping connector, the blind flange or protector flange may be removed and the membrane cut out or tapped by using conventional tapping tools. In this regard, the convex profile of the membrane allows conventional tapping tools to be employed with easy removal of chips.